Pre-charged Firing Cell for Inkjet Printhead Compatibility
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Solution Overview
Problem
The transition to updated manufacturing processes for electronic components in inkjet printing systems poses challenges in maintaining compatibility with previous products, leading to potential operational issues and inefficiencies.
Innovation Solution
A pre-charged firing cell design is implemented, utilizing a high voltage input signal for pre-charging and low voltage logic circuitry for selective discharge, with attenuator circuitry to manage high voltage inputs, ensuring reliable ink ejection through a firing resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If updated manufacturing processes are used to create electronic components, then manufacturing efficiency and cost are improved, but compatibility with previous products deteriorates
Solution Approach 1:
The patent changes the voltage parameter from high voltage to low voltage in the firing cell circuitry. This parameter change allows the use of updated CMOS manufacturing processes while maintaining compatibility with existing printhead designs and ink ejection functionality, thereby resolving the contradiction between manufacturing efficiency and product compatibility
2Power
If high voltage signals are used for ink ejection, then ejection power is improved, but risk of spurious firing and thermal run-away increases
Solution Approach 1:
The patent implements a pre-charged firing cell where capacitors are pre-charged to the required voltage level before firing. This preliminary charging action allows the system to maintain high ejection power when needed while avoiding continuous high voltage exposure that causes spurious firing and thermal run-away, thus improving firing stability
Solution Approach 2:
The system uses periodic charging and discharging of capacitors rather than continuous high voltage application. The firing cell is charged during idle periods and discharged only when ink ejection is required, reducing the overall time exposed to high voltage and preventing thermal run-away conditions
3Adaptability or versatility
If low voltage logic circuitry is used, then manufacturing compatibility is improved, but ability to drive high voltage firing resistor deteriorates
Solution Approach 1:
The patent introduces capacitors as intermediary energy storage elements between the low voltage logic circuitry and the high voltage firing resistor. The capacitors are charged from low voltage sources and then discharge to provide the necessary high voltage pulses to the firing resistor, enabling manufacturing compatibility while maintaining firing capability
Solution Approach 2:
The patent replaces direct high voltage electrical switching with a capacitor-based energy storage and release mechanism. This substitution allows low voltage CMOS logic to control high power firing events through electrical field management rather than direct high voltage switching, achieving both manufacturing compatibility and adequate firing power
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the operational efficiency and frequency of ink ejection in inkjet printing systems, preventing spurious firing and thermal run-away situations, while maintaining compatibility with previous manufacturing processes.
Implementation Method 1
a firing resistor causes droplets of ink within a vaporization chamber on the die to be ejected
Implementation Method 2
The firing cell operates using a high voltage input signal that pre-charges the cell during a pre-charge cycle and low voltage logic circuitry that selectively causes the firing resistor to be energized during a selective discharge cycle
Data Source
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AI summary
A printhead (40) comprises a firing resistor (52), a switch (72) connected to a node (76) and configured to control current through the firing resistor (52), pre-charge transistor (74) configured to pre-charge the node (76) during a pre-charge cycle responsive to a pre-charge signal (PRE) providing a voltage pulse across the pre-charge transistor (74) to the node (76) to a pre-charge voltage level that is sufficient to turn on switch (72), and a first transistor having a first terminal connected to the node (76) and a second terminal connected to a reference potential and configured to selectively discharge the node (76) to the reference potential during a discharge cycle when a select signal (SEL) has a level to turn on the first transistor.